The present invention relates to terminally functional polymers known as macromolecular monomers and to an improved process for their preparation.
The preparation of macromolecular monomers has been described in U.S. Pat. No. 3,786,116, which is incorporated in its entirety herein.
The process for preparation involves the anionic polymerization of, for example, styrene with or without capping the polystyrene with ethylene oxide, followed by the termination of the polymer with a halogenated compound containing a polymerizable moiety to form macromolecular chains terminated with the polymerizable moiety. This process leads to the formation of alkali metal chloride as byproduct. Although the process works with sodium or potassium initiators, it does not work well when a lithium initiator is used.
The patent teaches two different synthetic methods leading to the formation of the macromolecular monomers. The first method involves the termination of polystyrene lithium with a halogen containing compound which also contains a polymerizable moiety, such as epoxy or styrene group. Unfortunately, the polystyryl lithium group reacts with the polymerizable group as well as the halogen group. This causes polymer dimerization and other undesirable side reactions. The second method involves converting the polystyryl carbanion into a lithium alkoxide anion by capping with ethylene oxide prior to the addition of the halogen containing compound. This terminating sequence is designed to render the living polymer less susceptible to reaction at the polymerizable functional group by converting the highly reactive polystyryl lithium to a less reactive and hence more selective lithium alkoxide intermediate.
In contrast to the polystyryl carbanions, the alkoxide anions were found to be generally unreactive with either part of the halogen containing compound, i.e., with either the halogen or the polymerizable group.